Distribution of Alligators in Response to Thermal Gradients in a Reactor Cooling Reservoir

Thomas
M. Murphy, Jr. and I. Lehr Brisbin, Jr.

Abstract

Seasonal changes in the distribution of American
alligators inhabiting heated and unheated portion of a large reactor cooling
reservoir were studied.Abundance
indexes, calculated from 4 years of daylight head counts conducted three times a
month, were combined with 1 year of weekly night-cruise counts of alligators
along the entire reservoir periphery.In
winter alligators congregated and remained active in the area of the heated
effluent, but, in the remainder of the reservoir, they entered a semindormant
state.Maximum abundance indexes in
the unheated areas occurred during the summer months, but the numbers in the
heated area were at a low.Water
temperature predicts the alligator abundance index better than air temperature
or photoperiod.Decreasing water
temperatures in the fall appeared to stimulate the movement of animals
throughout the reservoir.Animals
that encountered warmer waters apparently restricted their movements to these
heated areas.